Studies is this proposal are directed to understanding the sequential biochemical and early ultrastructural events induced by methyl mercury in the cerebellum, in situ; in isolated cerebellar perikaryal cells and cell-free protein translation systems. Our studies have revealed both in vivo and in vitro methyl mercury inhibition of cell-free translation at the level of elongation. We will elucidate the molecular locus of this defect in the process of elongation using reconstitution experiments with the elongation factors (eEF-1 and eEF-2) following their isolation and purification. An early defect in cerebellar granule cell RNA synthesis requires determination of the significance of this molecular locus with especial reference to [3H]-uridine uptake, phosphorylation reactions and sensitivity of the individual RNA polymerases to methyl mercury after in vivo and in vitro intoxication. These biochemical studies will be correlated with stereologic morphometry of Purkinje and granule cell ultrastructure in vivo and also is isolated cerebellar perikaryal cell preparation after short term culture in the presence of methyl mercury. Identification of the mercurial induced biochemical and ultrastructural lesions will provide a means for assay of sub-symptomatic neurotoxicity and lead to a more rational treatment protocol. Mercurial interaction with the process of elongation will increase our understanding of this biochemical sequence in eukaryotic brain translation, its regulation and role in initiating cell injury.